Fluorescence resonance energy transfer (FRET) enables photosynthetic light harvesting1, wavelength downconversion in light-emitting diodes2 (LEDs), and optical biosensing schemes3. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells4, non-contact chromophore pumping from a proximal LED5, and markedly reduced gain thresholds6. However, the fastest reported FRET time constants involving spherical quantum dots (0.12–1 ns; refs 7, 8, 9) do not outpace biexciton Auger recombination (0.01–0.1 ns; ref. 10), which impedes multiexciton-driven applications including electrically pumped lasers11 and carrier-multiplication-enhanced photovoltaics12, 13. Few-monolayer-thick semiconductor nanoplatelets (NPLs) with tens-of-nanometre lateral dimensions14 exhibit intense optical transitions14 and hundreds-of-picosecond Auger recombination15, 16, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that interplate FRET (∼6–23 ps, presumably for co-facial arrangements) can occur 15–50 times faster than Auger recombination15, 16 and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies.
http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4231.html
Nature Materials (2015) doi:10.1038/nmat4231